I enjoy history, is this subject worth doing next year (I'm currently in year 10). Or is it a subject that you can pick up for 3/4?
1/2 is interesting, but not necessary for 3/4. 1/2 is generally about the 20th century and you cover a lot of different topics (we did the fall of the traditional order as a result of WW1, Nazi Germany, the Cold War, and a few others). In 3/4, you tend to go into one area in depth - for example, with Revolutions 3/4, Unit 3 is about the Russian/French/Chinese/American Revolution and Unit 4 is about another of those revolutions. If your school offers it, you can also do Renaissance Italy 3/4 or Australian History 3/4 instead of Revolutions. You don't really cover the content of those in 1/2.
I guess 1/2 helps in terms of skills (like historiography), but the actual content in 3/4 is mostly different.
History also has a lot of reading involved, so you might want to consider doing the 3/4 in year 11.